The invention relates to a piston-operated internal-combustion engine having wet cylinder liners whose collars are each arranged in the cylinder block and crankcase in a sunk manner, the bearing eye of the connecting rod pertaining to each cylinder on the side of the crankshaft being wider than the inside diameter of the cylinder liner, and the piston / connecting rod assembly which is assigned to each cylinder being mountable and dismountable only together with the pertaining cylinder inner as a unit. The invention has the purpose of facilitating the mounting and servicing of a piston-operated internal-combustion engine, whose cylinder liners are installed with an interference fit in the cylinder block and crankcase.
A piston-operated internal-combustion engine of this type is known from EP 0 140 894 B1. The mounting and dismounting of a unit consisting of the cylinder liner and a piston / connecting rod assembly take place by means of a radially expandable tool which is inserted into the cylinder bore. The axial force for the tearing-off of a cylinder liner required for the dismounting is to be transmitted to the cylinder liner by means of the frictional engagement between the tool and the cylinder bore. The radial force required for the frictional engagement is generated by the expanding of the tool. However, the radial force causes an expanding of the thin-walled cylinder liner in the area of the tool. In this manner, the cylinder liner, by means of the expanded tool, also is braced with respect to the cylinder block and crankcase. The axial force which is required for the dismounting of a cylinder liner installed with an interference fit and which is very large anyhow continues to increase undesirably and makes a dismounting by means of the devices of the known arrangement impossible.
When a unit is demounted, a part of the force for the tearing-off of the cylinder liner is to be generated by moving the piston against the tool. The force exercised by the piston on the tool braces itself against the cylinder block and crankcase by means of different engine components, such as the pin bearings, the connecting rod bearings and the crankshaft bearings. The concerned engine components are very sensitive to static loads so that it cannot be excluded that unnoticed damage occurs during the dismounting of a unit.
During the mounting of a unit, the piston / connecting rod assembly is to be held in position with respect to the cylinder liner by means of a partial vacuum between the tool and the piston. The tightness, which can be achieved by means of the piston rings of the piston, however, is insufficient for maintaining a sufficient vacuum over the duration of the mounting. Relative movements between the cylinder liner and the piston / connecting rod assembly during the mounting cannot be excluded and may result in unnoticed damage to engine parts, which would lead to their premature failure.
It is therefore an object of the invention to provide, for a piston-operated internal-combustion engine of this type having wet cylinder liners and whose piston / connecting rod assemblies can be mounted as a unit only together with the pertaining cylinder liners, a configuration of components by means of which the mounting of the units is simplified and safer, the dismounting of each unit is facilitated, and a damaging static loading of engine parts during the dismounting of a unit is avoided.
According to the invention, this object is achieved by providing an arrangement characterized in that, at the end of the collar of each cylinder liner on the cylinder head side, an external thread is arranged which is concentric with respect t to the collar, that the external thread, with respect to the outer diameter of the collar of the cylinder liner has a smaller outer diameter while forming a plane surface which points to the cylinder head, and in that each piston has a device arranged in the piston head for the application of a load lifting device.
Preferred embodiments of the invention are characterized by the following features:
i that the device for the application of a load-lifting device consists of at least two enlarged sections which, at the edge of a combustion chamber recess of the piston, project radially toward the inside; and PA1 ii the device for the application of a load lifting device consists of at least one threaded blink hole arranged axially in the piston head.
The advantages achieved by means of the invention are, in particular, that a highly loadable mechanical connection can be established between a mounting arrangement and the cylinder liner, that a deforming of the cylinder liner through the use of the mounting arrangement is excluded, that, during the dismounting of a unit, no static loading of engine components takes place, and that, during the mounting or dismounting, a reliable and stable connection exists between the mounting arrangement and all parts of a unit.
An embodiment of the invention is shown in the drawing and will be described in detail in the following.